1. Technical Field
The present invention relates to imaging apparatus, such as printers or copiers, having removable trays for sheet media.
2. Background Art
Copiers and printers often provide one or more removable sheet supply trays. Sheet supply trays are typically dedicated to a specific sheet size. For example, one tray may be designed to hold 8.5 inch by 11 inch sheets, another may hold 11 inch by 17 inch sheets, and yet another may hold A4 sheets, which are 210 mm by 297 mm. Unfortunately, the operator and the service personnel must have a selection of supply trays in order to utilize a variety of sheet sizes. This puts a storage and cost burden on the user, and increases the number of parts that service personnel must carry from customer to customer. It is therefore desirable to have a supply tray capable of holding multiple sheet sizes.
Typical sheet supply trays are often designed as an open-top box. Sheets are loaded into the tray by inserting them through the top of the tray and orienting the sheets so they are pressed against alignment features within the tray. When the tray is inserted into the imaging apparatus, the alignment of the sheets to the media transport mechanism of the imaging apparatus is affected both by the alignment of the receiver sheets to the tray and by the alignment of the tray to the media transport mechanism. In order to satisfy alignment requirements for the media transport mechanism, tolerances for the tray must be closely controlled. It is desirable to reduce the complexity of the imaging apparatus and the tray by reducing the buildup of alignment tolerances between sheets, tray and imaging apparatus. These alignment tolerances result in complex trays which have added manufacturing cost that increase the overall cost of owning the imaging apparatus. Therefore, it would be beneficial to reduce the complexity and cost of the tray.
The imaging apparatus may also determine which size sheet is loaded in a tray by mechanical or optical methods. Mechanical methods include holes, ribs or other tactile features which are part of a tray. Such tactile features engage sensors in the imaging apparatus, whereby the imaging apparatus determines information about the sheets that are loaded into the tray. Optical methods include presence or absence of optically detectable marks, location of marks, or bar codes which are detected using optical sensors. The imaging apparatus then determines information about the sheets loaded into the tray by the signals from the optical sensors, and adjusts its operation accordingly. Both mechanical and optical identification methods are inflexible, in that once a tray is marked or encoded, it is difficult for an operator to modify the marking. Thus a tray capable of holding a multiplicity of sheet sizes could not easily utilize mechanical or optical marking methods to indicate to the imaging apparatus information about the receiver sheets that are loaded in the tray. Furthermore, sensors for mechanical and optical marks tend to be more expensive than other sensor types. Therefore, it is desirable to have a flexible tray marking method capable of an unlimited number of user-adjusted changes of the marking. The flexible marking method should also be more economical to implement than alternative methods.